A light emitting diode (LED) is a semiconductor light emitting device composed of compound semiconductors and capable of realizing various colors, and is used as a general light source and a display light source, particularly, as a light source for IT devices including mobile phones. The light emitting diode has a much smaller size than typical light sources and market share thereof is rapidly expanding due to good properties in terms of low power consumption, rapid response and long lifespan. With expansion of applications of light emitting diodes, there is an increasing need for high brightness and high efficiency micro-pixel LEDs and novel displays, which can replace low brightness LED products such as typical full LEDs having problems of low efficiency and low pixel density in the display market. Particularly, with increasing demand for blue and white light emitting diodes with high efficiency as backlight sources for mobile displays, there is an increasing need for development for such LEDs.
Such a light emitting diode is generally formed of Group III-V nitride-based compound semiconductors, which have a direct transition type large energy band-gap so as to convert energy generated upon recombination of electrons and holes into light. Since the light emitting diode formed of the Group III-V nitride-based compound semiconductors can emit light in substantially the entire wavelength range depending upon the composition of the nitride-based compound semiconductors and can perform blue laser oscillation, various attempts have been made to develop a high pixel density and high efficiency light emitting diode based on such characteristics of the light emitting diode.
In a conventional technique for realizing white light using a light emitting diode capable of emitting various colors, phosphors are provided to the light emitting diode in order to realize a certain color through excitation thereof. However, the light emitting diode including the phosphors has a poor color rendering index (CRI), which indicates a poor degree of color realization of a certain object when illuminated with light, and provides different color rendering indexes depending upon current density, thereby making it difficult to secure color stability due to difficulty in regulation of color temperature and color rendering index which are main factors determining quality of a light source for illumination. Moreover, a conventional technique using quantum dot phosphors has a problem of deterioration in reliability due to low physicochemical stability, despite advantages of a wide selection width of wavelengths and improved luminous efficacy through high quantum efficiency.
Therefore, there is a need for development of a light emitting diode capable of realizing a high pixel density and high efficiency display without using phosphors.